Reactive scattering of a supersonic fluorine-atom beam: F + C₂H₅I, C₃H₇I, (CH₃)₂CHI

Abstract

Reactive scattering of F atoms with C₂H₅I, C₃H₇I and (CH₃)₂CHI molecules has been studied at an initial translational energy E ≈ 38 kJ mol^-1 using a supersonic beam of F atoms seeded in He buffer gas. Centre-of-mass angular distributions of IF scattering show peaking in the forward and backward directions, which is consistent with reaction via persistent F-I-C₂H₅, F-I-C₃H₇ and F-I-CH(CH₃)₂ complexes with lifetimes greater than two rotational periods. The extended microcanonical theory indicates that the angular distribution of reactive scattering for F + C₂H₅I arises from a range of transition state configurations generated by internal rotation about the extended C-I bond. The reactive scattering for F + C₃H₇I arises from a wide range of transition-state configurations, with sharply peaked forward and backward scattering from extended configurations and mildly peaked scattering from more contracted configurations. However, the range of transition-state configurations is much more limited for F + (CH₃)₂CHI. This distinction confirms the persistence of significant C-I bonding, which restricts the rotation of the IF and C₂H₅, C₃H₇ or (CH₃)₂CH fragments in these product transition states.